Burner control apparatus



June 5, 1934. f L. M PERSONS 1,962,095

BURNER CONTROL APPARATUS Filed Feb. 19, 1934 fh n /z /4 L 1 LocKouT a| [coMusTloN SWITCH I THERMAL- A 36 (fa/0 cuTouT v /5 swlTcH |EZ 50 'Room THERMOST l l J IGNITION CURRENT SUPPLY- Patented 'June 5, 1934 PATENT: OFFICE@ BURNER CONTROL APPARATUS Lawrence M. Persons, Des Moines, Iowa, assignor to Penn Electric Switch Co., Des Moines, Iowa,

a corporation of Iowa Application February 19, 1934,.Seral No. 711,925 l 3 Claims. `(Cl.` 158-28) The object of my invention is to provide a burner control apparatus which is simple, durable and comparatively inexpensive to manufacture.

A further object is to provide a burner control apparatus in which a switch serves both as a lockout and a thermal cutout or overload switch for the purpose of locking the apparatus against operation in case of either initial combustion failure or combustion failure after combustion has been 16 established and for. opening the circuit in case of an electrical overload-through the switch.

Still a further object is to provide a lock-out switch having a resistance or heater element and a combustion switch for partly shunting it out of l5 the power circuit to prevent operation of the lock-out switch under normal conditions but permit its operation when the power current flowing through the lock-out switch increases above a normal -value, thus protecting the circuit against 26 an overload as well as protecting the burner apparatus against combustion failure.

With these and other objects in view my invention consists in the construction, arrangement and combination'of the various parts of my device, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawing, in which:

Figure 1 is an electrical diagrammaticl view showing my control apparatus in normal position before the power circuit is established by a room thermostat or other controlling device.

Figure 2 'is an electrical diagrammatic view of a lock-out and thermal cutout switch inl its S tripped position caused by either combustion failure or electrical overload in the circuit; and' Figure 3 is an electrical diagrammatic view of a combustion' switch of theapparatus with the parts in the position they assume after combustion-has beenestablished; y

On the accompanyingv drawing, 1 have used the reference'numeral 10 to indicate a control panel. Mounted thereon area combined lock out and thermal cutout switch 12'and a combus- 46 tion switch 14. The combination switch 12 comprises contacts 16, one of which is carried by a spring arm 18. This arm is normally in position for closing the contacts 16, but may be tripped to circuit opening position by a pivoted cam 26 6c having a spring 22 urging ittoward tripped position. For retaining the cam 20 in normal position, a bimetal. latch 24 is provided and it is responsive to heat of a resistance or heater element 26.

The combustion switch 14 includes a ratchet wheel 28 mounted on a shaft 36, the shaft being connected with a bimetal coil 32. The coil 32 is mounted in the furnace stack or any other position responsive to combustion conditions for rotating the ratchet wheel 28.

The combustion switch includes contacts 34, one of which is carried by a spring arm 36 contacting with the periphery oi the ratchet wheel 28. Thus when the switch is cold as in Figure 1, the contacts 34 are separated, while a rise of temperature aiecting the bimetal coil 32 will rotate the ratchet wheel clockwise and close the con-1 tacts as in Figure 3.

The closing will occur immediately upon rota" tion of the ratchet wheel and after the contacts are closed, the ratchet wheel will slip relative to /the spring'arm 36. Likewise, when combustion fails, the ratchet wheel will immediately separate the contacts 34 and thenslip past the spring rarm 36. f

The switches 12 and 14 are included in a burner circuit as illustrated in Figure l. The contacts 34, it will be noted, shunt the resistance or heater 26, and in series with the contacts 34, I provide a second resistance 38 which performs a very important function in my apparatus.

Practical'operation In the operation of the controlling apparatus illustrated, when the room thermostat calls for heat, contacts in it close for thus establishing a circuit from the current supply through a terminal L1, through the contacts 16 of the switch 12,- through the heater'26 and then through the room thermostat to the burner motor and ignition mechanism to the terminal L2 connected with the other side of the current supply. This causes the burner motor and the ignition mechanism to operate, suitable switches, which form no part of my present invention, being provided for terminating the energization of the ignition :mecha- -nism automatically.

lcombustion is not established, the switch 12 y acts as a safety or lock-out switch by the heat radiated from the heater 26 warping the bimetal load.

It is thus obvious that the heater 26 functions both for the purpose of tripping the switch 12 upon combustion failure or upon current overload while combustion is in progress.

The relative resistance of the elements 26 and 38 is designed so that the currentthrough the heater 26 will nearly trip the switch l2 while nor- -mal current is flowing through the circuit, thus causing the switch to be tripped when slight additional current flows.

When combustion does not occur or when it fails, all the current must flow through the heater 26 because of the contacts 34 becoming separated instead of part of itflowing through the resistance 38, thus resulting in an increase of heat in the heater 26 sufficienty to trip the switch 12. It is thus obvious that the resistance 38 can be designed of the proper value for operation in various circuits as required. By using the resistance 38 to shunt the heater 26, the necessity of providing a thermal cutout or overload switch independent of the switch 12- is eliminated, the switch 12 thus serving both for combustion establishment lock-out service as well as overload circuit opening service. To operate as described, the

l heater 26 must have a substantial percentage of the normal power current flowing through it so that it can`respond with the required promptness to an overload current.

With respect to the relative resistance values `of the heater 26 and the resistance 38, I have found that they should be substantially equal. The resistance value of the heater 26 can vary greatly. The size of the motor, the characteristics of the bimetal element 24, the proximity of the heater to the bimetal element, the method of enclosing the heater and the element, the time period in which the lock-out switch is to operate because of initial combustion failure and other factors must all be taken into consideration. Regardless of the required resistance value for the heater 26 in order that it can perform its function as a lock-out switch on initial combustion failure within the prescribed period of time, the resistance value of the resistance element 38 should be substantially equal thereto. 'I'hus when the combustion switch closes, the current will divide in substantially equal portions to pass through the heater 26 and the resistance 38. This causes substantially half of the current to now through .the heater 26 so that a one-hundred percent overload on the burner apparatus will operate the thermal cutout switch in substantially the same period of time that it operates as a lock-out switch. Less than a hundred percent current overload will operate the combined lockwout and thermal cutout switch in its overload capacity, however, although, of course, it will take alonger period of time than when there is a hundred percent overload.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modiecl forms of structure or use of mechanical equivalents, which may be reasonably included within their scope.

I claim as my invention:

1. In combination with a burner motor, a control systern therefor comprising a main control switch, a combustion responsive switch open in the absence of and closed in the presence of combustion, a combined thermal time-limit and overload cutout switch having a resistance heater element and a warp element operable to open said last mentioned switch when heated to a predetermined temperature, a resistance of such Value that when connected in parallel with said heater element it renders the current flow therethrough just insufficient to operate said cutout switch during normal current flow and atcircuit including said main control switch, cutout switch and motor in series with said heater element connected in parallel with said combustion switch and resistance in series, whereby upon a material overload in said circuit, said cutout switch will open in a relatively short time.

2. In combination with a burner motor, a control system therefor comprising a main control switch, a combustion responsive switch open in the absence of combustion and closed in the presence of combustion, a combined time-limit and overload cutout switch having electro responsive means operable to open said last mentioned switch when said electro responsive means is energized for a predetermined period of time by a current flow of a predetermined value, a resistance of such value that when connected in parallel with said electro responsive means it renders the current flowing therethrough insuiiicient to open said cutout switch during normal current flow and a circuit including said main control switch, said cutout switch and said motor in series with said electro responsive means connected in parallel with said combustion switch and said resistance in series, whereby -upon flow of overload current in said circuit, said cutout switchl will open after a period of time of such flow.

3. In combination with a burner motor, a control system therefor comprising a main control switch, a combustion responsive switch open in the absence of combustion and closed in the presence of combustion, a combined thermal timelimit and overload cutout switch having a resistance heater element and a warp element operable to open said last mentioned switch when heated to a predetermind temperature, a resist- .ance of substantially the same resistance value as the resistance value of said heater element, whereby when connected in parallel with said resistance heater element, it renders the current flow therethrough insufficient to operate said cutout switch during normal current flow and a circuit including said main control switch, cutout switch and motor in series with said resistance heater element connected in parallel with said combustion switch and resistance in series, whereby upon an overload in said circuit, said cutout switch will open after a period of time.

LAWRENCE M. PERSONS. 

